==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.3.2
- Deployed with iRedMail Easy or the downloadable installer? downloadabel installer
- Linux/BSD distribution name and version: Ubuntu 20.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I setup mailing list so that "Who can send email to this list: Users under same domain."

BUT even if I use other domain emails, I can send to the mailing lists.  I don't want to restrict to members only, since I want to our users to send to the mailing list who are non members.  But I want only domain-users to be able to send.  Not other domain users.  For example, I can use a Gmail account to send to user1@example.com even though I setup "users under same domain."

Please help.